The purpose of this research is to study various spatial, temporal, and adapting effects in the visual system psychophysically. Specific experiments have been designed for the further elucidation of questions concerning the mechanisms of spatial and temporal summation and interaction with respect to where in the nervous system psychophysically measurable effects are determined. Response latency measurements will be used as a tool to determine basis and locus of psychophysical response at suprathreshold levels. Various adaptation conditions will serve as a means of modifying the background conditions against which specific variation in the spatial and temporal characteristics of the stimulus is evaluated.